The present invention relates to a method and an apparatus for following a vehicle in which a vehicle is able to follow a preceding vehicle running ahead in an automatic fashion while maintaining an appropriate distance therefrom.
Some typical examples of a vehicle distance measuring apparatus usable for following a vehicle are disclosed in Japanese Patent Publication Nos. 63-38085 and 63-46363. The apparatuses disclosed therein commonly have a pair of first and second parallel optical systems having two convex lenses 101, 102 disposed in a horizontally aligned relation at a prescribed distance L away from each other, as shown in FIG. 4. A pair of separate image sensors 103, 104 are horizontally disposed at the focal points of the lenses 101, 102 spaced a focal distance f from the locations of corresponding lenses 101, 102, respectively, for generating respective image signals to a common signal processor 120. The signal processor 120 successively shifts the image signals from the image sensors 103, 104 and electrically superposes them one over the other, so that the distance R from the lenses 101, 102 to an object 121 is calculated based on the principle of triangulation using the following formula: EQU R=(f.times.L)/d (1)
where d is a shift distance by which the image signals are moved to obtain the best match.
On the other hand, a typical method for following a preceding vehicle using an image sensor or the like is disclosed in Japanese Patent Publication No. 60-33352. In this method, for the purpose of following a target on a display screen, an operator has to set a following gate or window on the display screen which encloses the target to be followed, while looking at the screen.
Although it has been considered to combine the vehicle distance measuring apparatuses as described above, which operate to successively detect the distance from a vehicle to a preceding vehicle using an optical distance measuring device equipped with an image sensor, with the above-described vehicle following method, it is almost practically impossible for the driver to form a window or following gate similar in configuration to the image of the preceding vehicle using a joy stick, a track ball, a mouse and the like while driving the vehicle, as described in Japanese Patent Publication No. 60-33352, particularly from a safety point of view.